Rous sarcoma virus 35S RNA has recently been shown to have a terminally repeated nucleotide sequene of 21 residues. The presence of an identical nucleotide sequence at both ends of the viral RNA suggests a mechanism for reverse transcription of the linear viral RNA into a circular proviral DNA molecule. We have proposed that the repeated terminal sequene of the viral RNA genome is also the nucleotide sequence present in the host cell DNA which functions as the site of integration of the proviral DNA. DNA sequence analysis studies will be cnducted to determine if reverse transcription of the viral RNA into cDNA proceeds in an ordered linear fashion by jumping from the 5' end of the template RNA to the 3' end. The possibility that the terminally redundant sequence in the viral RNA is also the integration site sequence will be examined by means of hybridization methods. Chemical synthesis of an icosadeoxynucleotide by triester methods containing the repeated nucleotide sequence is planned. This molecule will be used to detect and isolate RSV integration sites in chicken DNA. Sequence analysis of host cell DNA sequence flanking the integratton site will be conducted. These sequencing studies are expected to reveal a promotor site in the host cell DNA which controls transcription of the integrated proviral genes.